Re: coherers (SSTC As a transmitter)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<evp-at-pacbell-dot-net>

> For filings I tried pure nickel, coin silver from a
> pre-LBJ quarter, and filings from a current nickel.  They need to be
> made as fine as possible, and Marconi recommended using a worn out
> file!  I washed everything with soap and water and then proceeded to
> file and file and file, but finally got enough of each to experiment
> with.  The silver seemed to work best, but all of them worked. 

I made some coherers with iron from nail and with stainless steel.
Filed with a grinding wheel and sorted from dust with a magnet.
The stainless steel filings work quite well, and don't oxidize.
A typical coherer requires a few volts for excitation. An interesting
fact that I could verify is that they switch to conduction in a few 
nanoseconds only.
The coherer action is too fast for something mechanical or thermal.

Antonio Carlos M. de Queiroz